X-rays negative on Alex Smith's thumb

X-rays taken immediately after Saturday's game on Alex Smith's right thumb were negative, according to a team source. Smith hurt the thumb while making a tackle after an interception. He threw one pass -- an incompletion -- on the following drive but was replaced by Shaun Hill midway through the drive. The 49ers will wait to see how Smith's thumb responds before determining his workload this week. The team's next game is Aug. 29 in Dallas.